Mu Yaxin, Zhuang Qianfen, Huang Saipeng, Hu Mingyue, Wang Yong, Ni Yongnian
College of Chemistry, Nanchang University, Nanchang 330031, China.
School of Chemical Engineering, Northwest University, X'ian 710069, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2020 Oct 5;239:118531. doi: 10.1016/j.saa.2020.118531. Epub 2020 May 26.
Adenine-stabilized carbon dots (A-CDs) are shown to be a viable fluorescent probe for highly sensitive detection and imaging of Cu. The probe has a linear fluorometric response in the 1-700 nM concentration range and a 0.3 nM detection limit. The probe, with excitation/emission maxima at 380/435 nm, is highly selective for Cu over other metal ions, anions, amino acids, and biomolecules. The fluorescence quenching mechanism of the A-CDs by Cu is investigated using transmission electron microscopy images coupled with elemental mapping, X-ray photoelectron spectroscopy, X-ray-excited Auger electron spectroscopy, fluorescence lifetime, UV-visible spectroscopy, and cyclic voltammetry. The experimental results show that the fluorescence quenching is caused by the combination of Cu-coordination-induced aggregation of the A-CDs, the reduction of Cu by the A-CDs, and the nonradiative photoinduced electron transfer process from the A-CDs to Cu or metallic Cu. The high sensitivity and high selectivity of the sensor are ascribed to the chemical interactions between the A-CDs and Cu, the photophysical process between the A-CDs and Cu, and the high fluorescence quantum yield of the A-CDs (44.6%). The A-CDs have excellent water solubility, good stability to variation of pH values, high photostability, fast response time, and low cytotoxicity. They are successfully employed for intracellular imaging of Cu in HepG2 cells and Cu detection in the tap water samples.
腺嘌呤稳定的碳点（A-CDs）被证明是一种用于高灵敏度检测和成像铜的可行荧光探针。该探针在1-700 nM浓度范围内具有线性荧光响应，检测限为0.3 nM。该探针的激发/发射最大值为380/435 nm，对铜的选择性高于其他金属离子、阴离子、氨基酸和生物分子。利用透射电子显微镜图像结合元素映射、X射线光电子能谱、X射线激发俄歇电子能谱、荧光寿命、紫外-可见光谱和循环伏安法研究了铜对A-CDs的荧光猝灭机制。实验结果表明，荧光猝灭是由铜配位诱导的A-CDs聚集、A-CDs对铜的还原以及从A-CDs到铜或金属铜的非辐射光致电子转移过程共同作用引起的。传感器的高灵敏度和高选择性归因于A-CDs与铜之间的化学相互作用、A-CDs与铜之间的光物理过程以及A-CDs的高荧光量子产率（44.6%）。A-CDs具有优异的水溶性、对pH值变化的良好稳定性、高光稳定性、快速响应时间和低细胞毒性。它们成功地用于HepG2细胞中铜的细胞内成像和自来水样品中铜的检测。
